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Rotational molding, also known as rotomolding , roto casting or spin casting, is a molding process for creating many kinds of mostly hollow items. More than 80% of all the material used is from the polyethylene family.
Typical products created in a rotational molding process include large volume water tanks, children's playgrounds, barricades and traffic cones. A heated hollow mold is filled with a charge or shot weight of the material, it is then slowly rotated causing the softened material to disperse and stick to the walls of the mold. In order to maintain even thickness throughout the part, the mold continues to rotate at all times during the heating phase and to avoid sagging or deformation also during the cooling phase.
Due to the large volume of most parts, a two-stage shredder granulator combination is commonly used when recycling rotomolded products such as water tanks. In this case, the shredders with their increased hopper volume are very well suited. Granulators of the PP、PE、PET series can be used as a single step solution or second stage grinder as well.
The pulverizers of the PNMP series play a very important role in the rotomolding process.
Firstly they are used to create the necessary power from the virgin Polyethylene pellets. Here a screening machine is used to create the right size, distribution and flow rate needed in the rotational molding process. Further, they can be used to create a powder from the regrind of recycled parts to be reused in the rotomolding process.